- ID:
- ivo://CDS.VizieR/J/AJ/160/81
- Title:
- 20 years of Beta CVn HIRES/APF radial velocities
- Short Name:
- J/AJ/160/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Uncovering the occurrence rate of terrestrial planets within the habitable zone (HZ) of their host stars has been a particular focus of exoplanetary science in recent years. The statistics of these occurrence rates have largely been derived from transiting planet discoveries, and have uncovered numerous HZ planets in compact systems around M-dwarf host stars. Here we explore the width of the HZ as a function of spectral type, and the dynamical constraints on the number of stable orbits within the HZ for a given star. We show that, although the Hill radius for a given planetary mass increases with larger semimajor axis, the width of the HZ for earlier-type stars allows for more terrestrial planets in the HZ than late-type stars. In general, dynamical constraints allow ~6 HZ Earth-mass planets for stellar masses >~0.7M{sun}, depending on the presence of farther out giant planets. As an example, we consider the case of Beta CVn, a nearby bright solar-type star. We present 20yr of radial velocities (RV) from the Keck/High Resolution Echelle Spectrometer (HIRES) and Automated Planet Finder (APF) instruments and conduct an injection-recovery analysis of planetary signatures in the data. Our analysis of these RV data rule out planets more massive than Saturn within 10 au of the star. These system properties are used to calculate the potential dynamical packing of terrestrial planets in the HZ and show that such nearby stellar targets could be particularly lucrative for HZ planet detection by direct imaging exoplanet missions.
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- ID:
- ivo://CDS.VizieR/J/A+A/617/A135
- Title:
- 20 years of photometric microlensing
- Short Name:
- J/A+A/617/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gaia DR2 offers unparalleled precision on stars' parallaxes and proper motions. This allows the prediction of microlensing events for which the lens stars (and any planets they possess) are nearby and may be well studied and characterised. We identify a number of potential microlensing events that will occur before the year 2035.5, 20 years from the Gaia DR2 reference epoch. We query Gaia DR2 for potential lenses within 100pc, extract parallaxes and proper motions of the lenses and background sources, and identify potential lensing events. We estimate the lens masses from Priam effective temperatures, and use these to calculate peak magnifications and the size of the Einstein radii relative to the lens stars' habitable zones. We identify 7 future events with a probability >10% of an alignment within one Einstein radius. Of particular interest is DR2 5918299904067162240 (WISE J175839.20-583931.6), magnitude G=14.9, which will lens a G=13.9 background star in early 2030, with a median 23% net magnification. Other pairs are typically fainter, hampering characterisation of the lens (if the lens is faint) or the ability to accurately measure the magnification (if the source is much fainter than the lens). Of timely interest is DR2 4116504399886241792 (2MASS J17392440-2327071), which will lens a background star in July 2020, albeit with weak net magnification (0.03%). Median magnifications for the other 5 high-probability events range from 0.3% to 5.3%. The Einstein radii for these lenses are 1-10 times the radius of the habitable zone, allowing these lensing events to pick out cold planets around the ice line, and filling a gap between transit and current microlensing detections of planets around very low-mass stars. We provide a catalogue of the predicted events to aid future characterisation efforts. Current limitations include a lack of many high-proper motion objects in Gaia DR2 and often large uncertainties on the proper motions of the background sources (or only 2-parameter solutions). Both of these deficiencies will be rectified with Gaia DR3 in 2020. Further characterisation of the lenses is also warranted to better constrain their masses and predict the photometric magnifications.
- ID:
- ivo://CDS.VizieR/J/AJ/141/17
- Title:
- 5-year spectroscopy and photometry of Deneb
- Short Name:
- J/AJ/141/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Deneb is often considered the prototypical A-type supergiant and is one of the visually most luminous stars in the Galaxy. A-type supergiants are potential extragalactic distance indicators, but the variability of these stars needs to be better characterized before this technique can be considered reliable. We analyzed 339 high-resolution echelle spectra of Deneb obtained over the five-year span of 1997 through 2001 as well as 370 Stroemgren photometric measurements obtained during the same time frame. Our spectroscopic analysis included dynamical spectra of the H{alpha} profile, H{alpha} equivalent widths, and radial velocities measured from SiII {lambda}{lambda} 6347, 6371.
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/38
- Title:
- 25-years photometry of V1057 Cygni
- Short Name:
- J/MNRAS/434/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The FU Orionis type of variable star (FUor), V1057 Cygni, underwent a nova-like outburst in 1969-1970. Among the FUors, V1057 Cyg is notable for having the most dramatic post-maximum decrease in brightness. Thus, photometric monitoring of this object is important for interpretations of the cause of this event. Here, we study the behaviour of V1057 Cyg over the last 25 years on the basis of our optical and infrared observations. The optical and near-infrared observations of V1057 Cyg started in 1974, and we present all our data (up to the end of 2011), including 1085 and 167 nights of optical and infrared photometry, respectively. The UBVRIJHKLM light curves for 1985-2011 show that despite the increased photometric activity, after a rapid decrease in brightness in the mid-1990s, the average level of brightness remained practically constant. After the object becomes fainter than V~11.5mag, a swerve appears in the track of the colour-magnitude diagram. The light variability shows a different periodicity in different spectral regions. We have discovered a period of 1631+/-60d in the BVR bands (1995-2011) and 523+/-40d in the RIJHK bands (2002-2011) with amplitudes of 0.5-0.3mag. The 523-d period is presumably correlated with the changes in the radial velocity of an emission component in LiI. We conclude that the observed properties of the FUor star V1057 Cyg are in accordance with current models of FUors involving binary or multiple systems.
- ID:
- ivo://CDS.VizieR/J/AJ/159/266
- Title:
- 12 years positional measurements of 8 binaries
- Short Name:
- J/AJ/159/266
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The orbits of eight systems with low-mass components (HIP14524, HIP16025, HIP28671, HIP46199, HIP47791, HIP60444, HIP61100, and HIP73085) are presented. Speckle interferometric data were obtained at the 6m Big Telescope Alt-azimuth Special Astrophysical Observatory of the Russian Academy of Sciences (BTA SAO RAS) from 2007 to 2019. New data, together with measures already in the literature, made it possible to improve upon previous orbital solutions in six cases and to construct orbits for the first time in the two remaining cases (HIP14524 and HIP60444). Mass sums are obtained using both Hipparcos and Gaia parallaxes, and a comparison with previously published values is made. Using the Worley & Heintz criteria, the classification of the orbits constructed is carried out.
- ID:
- ivo://CDS.VizieR/J/AJ/161/157
- Title:
- 10 years radial-velocity monitoring of Vega with TRES
- Short Name:
- J/AJ/161/157
- Date:
- 18 Jan 2022
- Publisher:
- CDS
- Description:
- We present an analysis of 1524 spectra of Vega spanning 10yr, in which we search for periodic radial-velocity variations. A signal with a periodicity of 0.676day and a semi-amplitude of ~10m/s is consistent with the rotation period measured over much shorter time spans by previous spectroscopic and spectropolarimetric studies, confirming the presence of surface features on this A0 star. The activity signal appears to evolve on long timescales, which may indicate the presence of failed fossil magnetic fields on Vega. TESS data reveal Vega's photometric rotational modulation for the first time, with a total amplitude of only 10ppm. A comparison of the spectroscopic and photometric amplitudes suggests that the surface features may be dominated by bright plages rather than dark spots. For the shortest orbital periods, transit and radial-velocity injection recovery tests exclude the presence of transiting planets larger than 2R{Earth} and most non- transiting giant planets. At long periods, we combine our radial velocities with direct imaging from the literature to produce detection limits for Vegan planets and brown dwarfs out to distances of 15au. Finally, we detect a candidate radial-velocity signal with a period of 2.43days and a semi-amplitude of 6m/s. If caused by an orbiting companion, its minimum mass would be ~20M{Earth}; because of Vega's pole-on orientation, this would correspond to a Jovian planet if the orbit is aligned with the stellar spin. We discuss the prospects for confirmation of this candidate planet.
- ID:
- ivo://CDS.VizieR/J/ApJ/877/60
- Title:
- YMGs. I. Young binaries & lithium-rich stars
- Short Name:
- J/ApJ/877/60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young stars in the solar neighborhood serve as nearby probes of stellar evolution and represent promising targets to directly image self-luminous giant planets. We have carried out an all-sky search for late-type (~K7-M5) stars within 100pc selected primarily on the basis of activity indicators from the Galaxy Evolution Explorer and ROSAT. Approximately 2000 active and potentially young stars are identified, of which we have followed up over 600 with low-resolution optical spectroscopy and over 1000 with diffraction-limited imaging using Robo-AO at the Palomar 1.5m telescope. Strong lithium is present in 58 stars, implying ages spanning ~10-200Myr. Most of these lithium-rich stars are new or previously known members of young moving groups including TWA, {beta}Pic, Tuc-Hor, Carina, Columba, Argus, ABDor, Upper Centaurus Lupus, and Lower Centaurus Crux; the rest appear to be young low-mass stars without connections to established kinematic groups. Over 200 close binaries are identified down to 0.2"-the vast majority of which are new-and will be valuable for dynamical mass measurements of young stars with continued orbit monitoring in the future.
- ID:
- ivo://CDS.VizieR/J/ApJ/726/18
- Title:
- Young intermediate-mass stars in W5
- Short Name:
- J/ApJ/726/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a survey of young intermediate-mass stars (age<5Myr, 1.5M_{sun}_<M*<=15M_{sun}_) in the W5 massive star-forming region. We use combined optical, near-infrared, and Spitzer Space Telescope photometry and optical spectroscopy to define a sample of stars of spectral types A and B and examine their infrared excess properties. We find objects with infrared excesses characteristic of optically thick disks, i.e., Herbig AeBe stars. These stars are rare: <1.5% of the entire spectroscopic sample of A and B stars, and absent among stars more massive than 2.4M_{sun}_. 7.5% of the A and B stars possess infrared excesses in a variety of morphologies that suggest their disks are in some transitional phase between an initial, optically thick accretion state and later evolutionary states. We identify four morphological classes based on the wavelength dependence of the observed excess emission above theoretical photospheric levels: (1) the optically thick disks; (2) disks with an optically thin excess over the wavelength range 2-24um, similar to that shown by Classical Be stars; (3) disks that are optically thin in their inner regions based on their infrared excess at 2-8um and optically thick in their outer regions based on the magnitude of the observed excess emission at 24um; (4) disks that exhibit empty inner regions (no excess emission at {lambda}<8um) and some measurable excess emission at 24um. A sub-class of disks exhibit no significant excess emission at {lambda}<=5.8um, have excess emission only in the Spitzer 8um band and no detection at 24um. We discuss these spectral energy distribution types, and suggest physical models for disks exhibiting these emission patterns and additional observations to test these theories.
- ID:
- ivo://CDS.VizieR/J/A+AS/139/393
- Title:
- Young Massive Star Clusters. II.
- Short Name:
- J/A+AS/139/393
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 4 lists photometric data for Young Massive Star Clusters identified in a sample of 21 nearby galaxies. The photometric data have been corrected for Galactic foreground extinction. Each cluster is identified by the abbreviated NGC number of its host galaxy and an object number: nxxx-yyy is object number yyy in the galaxy NGC xxx. Effective cluster radii have been obtained by modeling the cluster images as MOFFAT15 functions convolved with the point-spread function measured on the CCD images.
- ID:
- ivo://CDS.VizieR/J/ApJ/695/511
- Title:
- Young massive stars in LHA 120-N 44
- Short Name:
- J/ApJ/695/511
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The HII complex N44 in the Large Magellanic Cloud (LMC) provides an excellent site to perform a detailed study of star formation in a mild starburst, as it hosts three regions of star formation at different evolutionary stages, and it is not as complicated and confusing as the 30 Doradus giant HII region. We have obtained Spitzer Space Telescope observations and complementary ground-based 4m uBVIJK observations of N44 to identify candidate massive young stellar objects (YSOs). We further classify the YSOs into Types I, II, and III, according to their spectral energy distributions (SEDs). In our sample of 60 YSO candidates, ~65% of them are resolved into multiple components or extended sources in high-resolution ground-based images.
